In recent years, contactless connector apparatuses and contactless connector systems using inductive coupling between coils, and power transmission apparatuses and power transmission systems provided with a contactless connector apparatus or a contactless connector system have been being developed for the purpose of wireless charging of mobile electronic equipment or EV equipment, such as mobile phones and electric cars. For example, the inventions of Patent Documents 1 to 3 are known as contactless power transmission systems.
A battery-powered device and a charging cradle of Patent Document 1 include: a charging cradle having a power supply coil connected to an AC power supply; and a battery-powered device to be mounted on the charging cradle and including an induction coil electromagnetically coupled to the power supply coil. A built-in battery of the battery-powered device is charged with power transmitted from the power supply coil to the induction coil. The power supply coil includes a planar inner coil, and a planar outer coil disposed outside the inner coil and on the same plane as the inner coil. The AC power supply to the charging cradle includes a switching circuit for changing between an inner coil active state where AC power is supplied to the inner coil and not supplied to the outer coil, and an inner and outer coil active state where AC power is supplied to both the inner coil and the outer coil. The AC power supply changes between the inner coil active state and the inner and outer coil active state by the battery-powered device mounted on the charging cradle, and transmits power to the induction coil of the battery-powered device. That is, the battery-powered device and the charging cradle of Patent Document 1 are characterized by changing between two active states to achieve optimal power transmission.
A contactless power transmission apparatus of Patent Document 2 is characterized in that the power transmission apparatus transmits power from a primary coil to a secondary coil in a contactless manner through an gap by using electromagnetic induction between a pair of coils opposite to each other, and the power transmission apparatus is provided with a plurality of planar coils at a primary side, and one or more planar coils at a secondary side, and the outer diameter of the secondary coil is smaller than the outer diameter of the primary coils. The contactless power transmission apparatus of Patent Document 2 is characterized by selecting an optimal coil from among the plurality of primary coils to achieve stable power transmission.
A wireless transmission system of Patent Document 3 is provided with a resonator for wireless power transmission, the resonator including a conductor forming one or more loops and having an inductance, and a network of capacitors having a capacitance and a desired electrical parameter and coupled to the conductor. In this case, the network of capacitors includes at least one capacitor of a first type having a first temperature profile as the electrical parameter, and at least one capacitor of a second type having a second temperature profile as the electrical parameter.
The principles of such contactless power transmission systems can also be applied to information transmission systems provided with a contactless connector apparatus, and to induction heating apparatuses such as IH cooking apparatuses.